This invention relates to fiber feeding apparatus and more particularly to improved apparatus for feeding air-borne fibers to carding machines and the like.
It has long been common to employ pneumatic means for supplying air-borne fibers to carding machines and machines for forming non-woven webs or fabrics. In practice, air-borne fibers are deflected from a primary overhead supply duct selectively into each of a plurality of vertically disposed fiber feeding chutes, the lower ends of which communicate with the inlets to the associated carding or web forming machines. Normally a supply of fibers is allowed to collect to a predetermined height in the upper end of each vertical chute above an opening roll, which draws fibers from the supply, as needed, and feeds them downwardly into a formation section in the lower end of the chute.
In order to provide a uniformly thick lap or web at the output of a vertical supply chute, it has been customary in the past to attempt to regulate the degree to which the fibers are compacted in the formation section of the chute, or in other words immediately prior to their being fed to the input of the associated machine. One such means for compacting the fibers in a supply chute is disclosed in U.S. Pat. No. 3,169,664, wherein a reciprocable piston is mounted in communication with the upper end of the formation section of the chute to supply pulses of compressed air which increase the compactness or density of the column of fibers located in the formation section. The piston works in cooperation with a flap valve, which is closed as the piston moves on its expansion stroke so that compressed air is built up within the chute, and which opens during the retraction of the piston so that fresh air is drawn into the chute above the compacted fibers. The effect of the piston is thus uni-directional, since it tends to compact the fibers upon its expansion stroke, but has no effect upon the fibers during its retraction.
In addition to the use of a reciprocable piston, it has been customary also to employ a pivotal bellows or vane pump, which is mounted on a vertical, fiber feeding duct with its discharge end communicating with fibers located in the lower end of the feed chute (for example in the formation section of the chute), thereby intermittently to compress the fibers in this section in a manner similar to that of the above-described piston.
Although these prior piston and bellows-type devices have been designed intermittently to compact the fibers located in the formation section of a feed chute beneath the associated opening roll, they have not been designed also to compact or densify the supply of fibers normally held in the surge section of the chute above the associated opening roll. Moreover, such prior piston and bellows-type devices have normally been positioned above the associated opening roll so as to discharge air pulses into the space between the chute wall and the associated opening roll, thereby increasing turbulence at the point of discharge of fibers tangentially from the feed roll, and also precluding the use of a re-entrant duct of the type disclosed, for example, in U.S. Pat. No. 4,240,180, for the purpose of providing adjustable, generally uniform air flow past the discharge point of the associated opening roll.
Moreover, heretofore there has been no satisfactory means for monitoring and controlling the operation of such prior art pump means in order to produce the desired density of the column of fibers formed in the formation section of a chute.
It is an object of this invention, therefore to provide an improved vane pump or bellows apparatus for compacting the fibers in the formation section of a feed chute of the type described, while at the same time producing a vibratory effect on the fibers located in the upper end or surge section of a feed chute, thereby to control the compaction of fibers in the chute.
A further object of this invention is to provide novel means for applying compaction pressure to the fibers in the lower end of a vertical feed chute, but without interfering with the air pressure in the vicinity of the associated opening roll.
Still another object of this invention is to provide electrical control means for controlling the rate of feeding and compaction of fibers in chutes of the type described, thereby to control the density of the webs produced at the outputs of such chutes.